bjoernager/rust
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Unconditionally capture tokens for attributes.

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This allows us to avoid synthesizing tokens in `prepend_attr`, since we
have the original tokens available.

We still need to synthesize tokens when expanding `cfg_attr`,
but this is an unavoidable consequence of the syntax of `cfg_attr` -
the user does not supply the `#` and `[]` tokens that a `cfg_attr`
expands to.
This commit is contained in:
Aaron Hill 2020-09-26 19:33:42 -04:00
parent 1eaadebb3d
commit b9b2546417
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GPG key ID: B4087E510E98B164
15 changed files with 153 additions and 120 deletions
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35
compiler/rustc_expand/src/config.rs
View file

@ -3,10 +3,13 @@
use rustc_ast::attr::HasAttrs;
use rustc_ast::mut_visit::*;
use rustc_ast::ptr::P;
use rustc_ast::token::{DelimToken, Token, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, LazyTokenStreamInner, Spacing, TokenStream, TokenTree};
use rustc_ast::{self as ast, AttrItem, Attribute, MetaItem};
use rustc_attr as attr;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::map_in_place::MapInPlace;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{error_code, struct_span_err, Applicability, Handler};
use rustc_feature::{Feature, Features, State as FeatureState};
use rustc_feature::{
@ -289,7 +292,37 @@ impl<'a> StripUnconfigured<'a> {
expanded_attrs
.into_iter()
.flat_map(|(item, span)| {
let attr = attr::mk_attr_from_item(attr.style, item, span);
let orig_tokens =
attr.tokens.as_ref().unwrap_or_else(|| panic!("Missing tokens for {:?}", attr));
// We are taking an attribute of the form `#[cfg_attr(pred, attr)]`
// and producing an attribute of the form `#[attr]`. We
// have captured tokens for `attr` itself, but we need to
// synthesize tokens for the wrapper `#` and `[]`, which
// we do below.
// Use the `#` in `#[cfg_attr(pred, attr)]` as the `#` token
// for `attr` when we expand it to `#[attr]`
let pound_token = orig_tokens.into_token_stream().trees().next().unwrap();
if !matches!(pound_token, TokenTree::Token(Token { kind: TokenKind::Pound, .. })) {
panic!("Bad tokens for attribute {:?}", attr);
}
// We don't really have a good span to use for the syntheized `[]`
// in `#[attr]`, so just use the span of the `#` token.
let bracket_group = TokenTree::Delimited(
DelimSpan::from_single(pound_token.span()),
DelimToken::Bracket,
item.tokens
.clone()
.unwrap_or_else(|| panic!("Missing tokens for {:?}", item))
.into_token_stream(),
);
let mut attr = attr::mk_attr_from_item(attr.style, item, span);
attr.tokens = Some(Lrc::new(LazyTokenStreamInner::Ready(TokenStream::new(vec![
(pound_token, Spacing::Alone),
(bracket_group, Spacing::Alone),
]))));
self.process_cfg_attr(attr)
})
.collect()

1
compiler/rustc_expand/src/expand.rs
View file

@ -1785,6 +1785,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
span: at.span,
id: at.id,
style: at.style,
tokens: None,
};
} else {
noop_visit_attribute(at, self)